Caffeine Safety in Pregnancy

by Alice Callahan on July 21, 2014

My first trimester of pregnancy coincided exactly with the last three months before my book deadline. I was lucky to have only mild nausea during this time, but I was really, really tired, especially in the afternoon. I tried hard to get enough sleep at night, but my body also seemed to want a 2-hour nap after lunch, when I just couldn’t stay awake, much less think and write. Pre-pregnancy, I responded to a post-lunch slump by pouring myself a cup of coffee or, even better, spending the afternoon at my favorite coffee shop, where a latte and the people around me helped keep me focused for a productive afternoon. A cup of herbal tea in the same atmosphere just made me want to curl up in one of the comfy chairs and take a nap, even as my caffeine-fueled coffee shop friends typed energetically around me.

But now I was pregnant, after 18 month of trying and several miscarriages, and I wanted to do all I could to minimize the risks of losing this pregnancy. In previous pregnancies I’d just given up most caffeine, and that wasn’t that hard to do. In this one, I was more afraid than ever of a miscarriage, but I also needed the caffeine boost more than ever to finish my book. I wanted to know what the research says about the safety of caffeine in pregnancy so that I could make an informed decision about whether to consume caffeine, and if so, how much.

In her book, Expecting Better, Emily Oster includes an excellent discussion of caffeine in pregnancy. I consulted this for a quick answer to my question, and her analysis of the research on this topic helped me feel comfortable strategically drinking a little coffee in the afternoon. However, as much as I respect and highly recommend Oster’s book, I’ve also found that my approach to risk in pregnancy is a bit more conservative, and as soon as I had the chance, I wanted to look at the studies myself.

Major sources of caffeine

Caffeine is found in coffee, soft drinks, tea, energy drinks, chocolate, and some medications and weight loss supplements. The table below gives caffeine content of many of these products so that you can estimate your own caffeine intake. Note that caffeine content of coffee and tea can vary quite a bit depending on type and preparation. For example, an 8 oz. serving of drip coffee has been measured to have anywhere between 70 and 280 mg of caffeine. My coffee shop makes every espresso drink with two shots of espresso, and they’re proud of their strong drinks. (My standard pregnancy order there is a half-caf latte.)

We know that caffeine crosses the placenta from the maternal to fetal bloodstreams, and the fetus can only slowly metabolize, or break down, caffeine. On top of this, maternal metabolism of caffeine is slowed in pregnancy, so caffeine lingers in mom’s bloodstream for longer time. The half-life of caffeine, or the time it takes for half of the caffeine to leave the bloodstream, is estimated to be 2-6 hours in older children and adults, 10-20 hours in pregnant women, and 4 days in newborn babies. (From a practical standpoint, this means that a cup of coffee might keep you awake longer than it did prior to pregnancy.)

So we know that when we consume caffeine during pregnancy, it enters the fetal circulation, but is this necessarily harmful? Animal studies show that high intakes of caffeine can cause birth defects, but these are very high intakes, and there’s no evidence of this occurring in humans. The main concern with caffeine in pregnancy is that it might increase the risk of miscarriage. However, this is one of those questions where there are lots of studies but also lots of confusion, making it an interesting case study in the limitations of research, particularly when it comes to pregnancy.

Can caffeine cause miscarriage?

There have been many studies of this question, but they all have serious limitations. A 2013 Cochrane review of caffeine safety in pregnancy only found one study that met its criteria, and it didn’t even address the miscarriage question. A 2004 review of papers published since 1966 identified 15 relevant studies but concluded that their methodological flaws were so great that they essentially couldn’t draw any conclusions from them. Why is it so difficult to study and answer this question?

The biggest problem is one that plagues almost all of pregnancy and parenting research: it is nearly impossible to do randomized controlled trials. Instead, we’re stuck with observational data. A cohort study, for example, would measure women’s caffeine intake early in pregnancy (usually by asking the women to estimate how much they consumed) and then track which women ended up miscarrying. If women who miscarried had consumed more caffeine than those who didn’t, then we could conclude that there is a correlation or an association between caffeine intake and miscarriage. However, this is not evidence that caffeine actually causes miscarriage. There are a number of problems with drawing conclusions from observational studies on caffeine use in pregnancy:

Confounding factors. In a randomized controlled trial, we could compare two or more groups of women who were otherwise very similar except in how much caffeine they consumed. But in the real world, and in observational studies, a variable like caffeine consumption doesn’t exist in isolation. For example, studieshavefound that women who consume more caffeine in pregnancy are also more likely to be smokers, to drink alcohol in pregnancy, and to be older – and any of these factors could also increase miscarriage risk. Researchers usually try to statistically control for these confounding factors, but we can never be sure if the statistical methods are adequate or if the information is accurate. (For example, some women might not tell the truth about smoking in pregnancy.)

Pregnancy symptoms. The biggest confounding factor is probably that pregnancy itself can affect caffeine consumption. Many women feel nauseous in the first trimester, and coffee, with its strong taste and odor, can lose its appeal during this time. Furthermore, women with greater symptoms of nausea and vomiting – the least likely to want a strong cup of coffee – are also less likely to miscarry. These symptoms seem to be a signal that the pregnancy is going well. Women who have a “missed” miscarriage, in which the fetus has stopped developing but mom’s body doesn’t naturally expel it right away, may find that their symptoms of nausea and vomiting have subsided before the miscarriage is discovered. Thus, women who consume more caffeine in pregnancy may already be at higher risk for miscarriage or may have already had one. While some studies have attempted to correct for this problem by asking women about their pregnancy symptoms, one woman’s “severe nausea” may be another’s “mild nausea.” It’s hard to quantify such a subjective variable or to account for changes in pregnancy symptoms over time.

Recall bias. The problem here is that most studies have asked women after a miscarriage may have occurred how much caffeine they consumed in early pregnancy, and women who have already experienced the trauma of miscarriage may remember their pregnancies differently from those who didn’t. I remember just as many details about a miscarried pregnancy 18 months ago than I do about the first trimester of this pregnancy, which ended just a few weeks ago. I’ve gone over the details of that lost pregnancy in my mind so many times that those memories are vivid and strong. To reduce recall bias, researchers need to ask women about their caffeine consumption as soon as they know they’re pregnant, before a miscarriage might occur, but most studies have not been conducted this way.

All of these sources of bias push the data in one way, tending to overestimate the association between miscarriage and caffeine consumption.

Two prospective cohort studies published in 2008 claimed to have overcome many of these limitations, but although their methods were improved, there was still lots of room for bias. Even more confusing, they came to different conclusions. One study led by David Savitz of Mount Sinai School of Medicine found no relationship at all between caffeine consumption before and during early pregnancy in more than 2400 women. The second study, led by Xiaoping Weng of Kaiser, tracked more than 1000 pregnant women and concluded that there was an increased risk of miscarriage associated with consuming more than 200 mg of caffeine per day, but not less than this. Interestingly, women with a history of miscarriage showed no association between caffeine and miscarriage, providing some reassurance for women like me and suggesting that in these cases, there are more important factors contributing to miscarriage risk.

Finally, a 2010 study led by Anna Pollack of Johns Hopkins did a nice job of avoiding many of the limitations mentioned earlier by asking women to keep daily diaries of caffeine, alcohol, and tobacco use during a full year, beginning before pregnancy. Like the Savitz study, this study found no relationship between caffeine and becoming pregnant or miscarriage. The problem is that it only included 79 women, 11 of whom miscarried, a sample size too small to answer this question with much certainty. None of these 3 studies included many women consuming more than 300-400 mg/day, limiting their ability to look at risks of those higher caffeine intakes.

In a 2010 Committee Opinion, ACOG concluded that 200 mg of caffeine per day or less probably doesn’t increase the risk of miscarriage, mostly based on the studies by Savitz and Weng. Given all of the potential sources of bias and the studies finding no association at all, this is a conservative recommendation. Chances are, consuming more caffeine (to an extent) probably won’t increase your chances of miscarriage, but ACOG errs on the side of caution.

Can caffeine cause preterm birth or affect birth weight?

For this question, we actually have good data. A clever randomized controlled trial recruited pregnant women who were already drinking at least 3 cups of coffee per day. The researchers randomized the women to two groups, and starting around 18 weeks of pregnancy, they gave one group regular instant coffee and the other decaf instant coffee (without telling them which they were receiving). The women were asked to drink this coffee at home but were allowed to have other sources of caffeine as they wished. The decaf group ended up consuming 177 mg/day and the caffeinated group consumed 317 mg/day. Despite this difference in caffeine intake, there was no difference in preterm births, birth weights, or Apgar scores. Thus, at least within this range of caffeine intake, there doesn’t appear to be a risk of these outcomes.

Information means better choices and less guilt

Some women will look at this research and decide they’ll just avoid caffeine altogether, as I did in previous pregnancies. If, in this pregnancy, the research showed a real risk to consuming a little caffeine, I’d certainly continue to avoid it. But the research shows that consuming 200 mg per day or less is not a risk, and more is probably okay. In my case, a cup of coffee or so per day was helpful in allowing me to remain productive throughout my first trimester. Regardless of our individual choices, it is important to be honest about the risks (or lack thereof) of caffeine in pregnancy, particularly for women who do experience pregnancy loss. Many wonder if it was their fault, and they deserve to know that their miscarriage most likely had nothing to do with caffeine.

Have you consumed caffeine in pregnancy? What information did you use to make this decision?

Thanks for this – very timely! Recently pregnant and was wondering what the research really says about caffeine. I now I have a preschooler who is sometimes dropping the afternoon nap so it is no longer an option for me to nap like I did first time round (was self employed from home) and I have started to become reliant on a coffee to get me through the occasional periods of extreme fatigue. Have stayed below 200mg per day but feeling less guilty now about having even that – thanks! Interestingly I have definitely become more susceptible to the effects of caffeine and didn’t realise this was normal in pregnancy – I could previously drink an espresso before bed no problem and never used to use it as a prop – was equally happy with a decaff! But today felt quite shaky after a morning long black that I had without ‘needing’ it!

Yeah, this slower metabolism of caffeine in pregnancy was news to me, but I think I notice a difference as well. A little seems to go a long way, but maybe that’s also because I’ve cut back in general. I didn’t look into this in depth, but review papers said that slower metabolism is most pronounced in late pregnancy.

I too felt very tired in early pregnancy, particularly towards the end of my first trimester and into the first couple weeks of my second trimester. I continued to consume 1 mug of coffee per day (approx. a cup and a half) after learning of my pregnancy. I probably consulted some online sources on the topic to confirm, but as I recall, the decision was based on my feeling that a little caffeine wouldn’t be harmful to the fetus and would be very helpful for me in terms of maintaining productivity during a period of excessive fatigue. My decision to continue consuming coffee in moderation was supported by a physician with whom I attended a prenatal yoga class. She said that it was shown to be safe, at least in small amounts. I think she cited the ACOG statement and/or its Canadian counterpart. I’m happy to say that my baby was born at term, with a very healthy birth weight. I loved my pregnancy – it was a joyous experience, notwithstanding the fatigue and mild nausea early on in the process.

I took a similar approach to you. When I was pregnant with my first, I wasn’t a coffee drinker, so avoidance was not a problem. By the time I was pregnant with my second, I was using it to stay awake at work (especially when I had to be put on supplemental progesterone due to dangerously low levels at 9 weeks). I just stuck with one, maybe two, cups per day. Even still, with all the progesterone I was taking, I was barely able to stay awake in meetings. It was rough.

I also drank it while breastfeeding- which you don’t go into here, but I’m curious about. Again, I stuck with the 1-2 cups per day.

I did the same with breastfeeding and I’m sure found some resources to reassure me about that, but I haven’t looked at this question since Cee was a baby. I’ll look at the research and write a separate post. Several readers have asked me about it!

It was interesting to me that studies that accounted for maternal age consistently found that caffeine intake increased with age. Maybe life just gets more tiresome the older we get, or maybe it is a taste thing?

For my first pregnancy, I would allow myself one soda/month. For my second, I allowed myself about 2-3 eight-ounce cups of coffee per month, but napped a lot while my daughter was napping or watching tv. I too am interested to know about drinking coffee while breast feeding. I couldn’t stand to drink coffee while pregnant, but have no adverse reaction to it while nursing.

I am a regular coffee drinker but only one expresso first thing in the morning. I kept this up through both pregnancies as well as breastfeeding. I did quite a bit of reading around it and came to the conclusion that the amount I was drinking would have minimal effects. I certainly didn’t notice any side effects with breastfeeding (always made sure to drink the coffee following a big morning feed).

When you did your research on this topic did you by any chance come across some proposed explanations on how could high doses of caffeine cause miscarriage or birth defects? What is the suggested mechanism? How about caffeine and breastfeeding? Are there any risks for the baby? Thank you.

Thank you for your awesome blog. I am glad that you are back to more regular posts now. Good luck with your book and fingers crossed that everything goes well with you and the baby.

Hi Tereza – Your question about mechanism is a great one. Interestingly, it’s basically not discussed in the human studies, which is disappointing. Animal studies have investigated several hypotheses, the most promising being caffeine’s interaction with adenosine, adrenergic, cholinergic GABA, or serotonin receptors. I didn’t research this very much, because these studies used very high doses and often inappropriate routes of exposure (like i.v. instead of oral). This is a thorough review with free full text: http://onlinelibrary.wiley.com/doi/10.1002/bdrb.20288/full

One mechanism that I read about was decreased blood flow to the placenta due to increased maternal epinephrine following caffeine consumption. Here’s an old study on that: http://www.ncbi.nlm.nih.gov/pubmed/6650631

Coffee was one of the few things that rarely made me throw up when I was pregnant, though I did switch over to decaf. I drink more tea than coffee, so I limited myself to a couple cups of caffeinated tea per day, and eventually just ended up buying decaf tea bags and living with the fact that it simply doesn’t taste as good. Sleeping was harder once I hit the second trimester, and I didn’t want to add to that with more caffeine. I didn’t worry too much about it; I’d read what most of the books say, that a couple cups of coffee a day are safe, so I just tried not to overdo it. My diet was limited enough with the vomiting and gestational diabetes that I figured the occasional hit of caffeine was fine.

Very informative! Thanks. I always try to avoid coffee (I don’t drink soda or eat much chocolate) as much as possible throughout the first trimester, but usually it’s easy enough as I suffer all-day morning sickness, but then typically ease up and allow myself a cup of joe in the mornings, or a half-caf latte in the afternoons. However, with this pregnancy I have sufferred terrible insomnia, that I have nearly avoided it all together. I have read before (in a study, but now I can’t find it) – that mom’s who drink caffeine in a limited amount and then breastfeed do not have an issue with their newborn taking in the caffeine through the milk because they have become used to it through the womb. If you went cold turkey during your pregnancy with caffeine, but then drink some while you are nursing, the caffeine will most likely affect your baby.

One of the studies I ran across during my research for this post found no significant effect of maternal caffeine consumption in pregnancy or during breastfeeding on infant night waking. Moms who drank more caffeine during both pregnancy and breastfeeding had a tendency to have babies that woke more often, but this wasn’t significant. (But also – chicken and egg, right? Do moms drink more caffeine because their babies wake more often during the night?) That study indicates that habituation doesn’t affect the baby’s response to caffeine.http://pediatrics.aappublications.org/content/129/5/860.full

However, another interesting study actually looked at physiology of near-term fetuses and found that maternal consumption of 300 mg of caffeine increased fetal wakefulness, movements, and heart rate variation, but only in those whose moms didn’t usually drink much caffeine, not those who did, suggesting that fetuses can become tolerant to caffeine. This was a small study (just 13 moms) but pretty cool. Maybe it is better to routinely drink a little caffeine per day than to abstain completely but then binge for an all-nighter.http://www.ncbi.nlm.nih.gov/pubmed/19506007

I’ll see what else I can find when I look at caffeine and breastfeeding, and let me know if you can find a study to support the habituation idea for breastfeeding. Thanks for your comment!

Hi! Thanks for such a thorough discussion! I went completely off caffeine for my first three babies. I also had two miscarriages during my no caffeine time. For my fourth baby, I was so tired I gave in and drank a big iced tea every afternoon and had no problems. I was a little more laid back by then but I still believe moderation is best. I worried a lot about water quality and lead in the pipes more than I did the caffeine and thought that was why I miscarried.

As always, thanks for such an informative post! I love the approach you take to these topics. I wasn’t drinking caffeine regularly until my third pregnancy, and found the suggestion to stay below 200 mg a day. I typically had one coke zero a day after about 20 weeks, once I could actually keep much of anything down. I’m interested in the breast feeding connection as well. I found when my baby was very new, if I had caffeine later in the day it seemed to coincide with the nights he was more wakeful, but now at ten months it doesn’t seem to matter.

I wouldn’t say I was cavalier about caffeine intake during my pregnancy, but because I was pretty happy with my healthcare providers and none of them issued stern warnings about it, I figured I could be flexible. If I remember correctly, I got a sheet of foods and substances to avoid, and I think it recommended a caffeine limit but not a proscription.

I took this to mean one cup of coffee per day, more or less. This plan went off the rails during the first trimester however, as I had no idea how dog-tired I’d be during the days. I started to add in a cup of black tea after lunch, but that didn’t seem to help me stay awake…even though the tea was caffeinated, it made me just want to curl up and snooze. (It also didn’t help that I was living in a place that started to get dark before 3p during the winter–something I wasn’t used to). I tried switching to black tea in the morning and coffee after lunch, and that seemed help a bit. I didn’t keep track of other caffeinated things I ate, like chocolate, and I don’t really drink soda.

I had no idea that the pregnant bodies process caffeine more slowly however. I had a few bouts of insomnia during my pregnancy, but I’d heard that was par for the course, though I’m sure my afternoon coffees didn’t exactly help.

My oldest was a micropreemie and received caffeine through her IV several times a day for months. It helped her central nervous system and her breathing, so I felt that a little caffeine in my second pregnancy was not a huge deal – crossing the placenta is still hard to compare to mainlining it!

I can only stomach one can of soda a day – more than that, or coffee in any form, and I get too jittery.

I am more worried about any effect that Caffeine has on brain development, specifically disorders such as ADHD. I have never come across a study that has looked into it. However, since people’s brains who have ADHD function better with stimulants it would seem logical that if a persons brain was being given stimulants while it was developing it would then “learn” to need those stimulants to function at its best. Not that there is any evidence of this.

A 2009 study also found no relationship between pregnancy coffee intake and ADHD in children. There initially appeared to be a relationship when mom drank more than 10 CUPS of coffee per day, but after adjusting for confounding factors, it was no longer significant. http://www.ncbi.nlm.nih.gov/pubmed/18764862

I didn’t read either study, but they look pretty decent and give me some reassurance that we don’t need to worry about moderate caffeine consumption and behavioral outcomes in kids.

I recently lost a pregnancy at 7 weeks, (even though we saw a heartbeat at 6 weeks). I have a 2 year old daughter and she’s not a good sleeper. In order to keep up at work, I increased my coffee consumption, and continued to drink 4-5 cups of brewed coffee. (I still do, and I know this has to stop). I often blame myself for having lost this pregnancy due to my careless caffeine consumption. In reality, I do not know whether it indeed caused it, and I know correlation does not mean causation, but I am determined to avoid it the next time around.

I’m so sorry to hear about the loss of your pregnancy, and I know from experience that your impulse is to look for something that you did wrong that could explain the loss. I didn’t get into higher amounts of caffeine consumption in this post because the studies just aren’t very good. At the higher ends of caffeine intake, there are fewer women, and the confounding factor of nausea is an even bigger problem. Oster discusses these data more in her book if you are interested (she was a serious coffee drinker so was more interested in those studies). We do know that most miscarriages are due to genetic mutations, and there is nothing we can do to prevent them from occurring. I hope you don’t blame yourself, but I also understand that it’s hard to be rational about things like this. Big hug to you and best of luck:)

After experiencing the brutal migraines of caffeine-withdrawal a few weeks into my first pregnancy back in 2008, I did some reading and was thrilled to discover that indeed a little bit of caffeine was safe in the first trimester. I haven’t looked back since! lol!

I drank one cup a day all through the pregnancy. It kept me from having the nasty withdrawl headaches, and, since the cafeteria at work was a 3 minute one-way walk across the factory, it also increased my daily exercise to have to go get it.
I had the same experience as many people here, the evidnece was inconclusive, the recomendations vary so dramatically from country to country…. The list I got from the ob-gyn was a laugh, so I ignored it. The list stated “Avoid green tea. There is no evidence that drinking green tea will not cause significant harm to the developing fetus”. Hmmm, one billion babies in China, and there is no evidence? I think it would be nice if health researchers from a multitude of countries pooled their base data, perhaps then we could have a significant sample size to make some reasonable statistical conculsions.

So many people have thanked you for this article but I’d like to add one more voice. Even disregarding its effects on wakefulness and productivity, I’ve found before becoming pregnant that caffeine has been very helpful in reducing my symptoms of constipation and a mood disorder (both of which, of course, tend to become more sever during pregnancy). After my hyperemesis gravidarum went into remission in the second trimester, I found that adding a small cup of coffee to my daily routine caused the greatest improvement to my quality of life of anything I did, including resuming a mostly normal diet and being able to leave the house. I even suspect that drinking a small cup of coffee every morning has reduced some of my nausea (maybe just because I’m avoiding withdrawal headaches). I’m very reassured to know that the thing that has helped me so much is not also putting my baby at risk! I can only imagine how much more difficult this pregnancy would have been had I decided to abstain.

Thanks very much for the concise and helpful post! It corroborates what I have recently learned, and I’m glad to know that my [albeit less] intake of coffee isn’t going to cause some crazy Sigourney Weaver ALIEN-style situation 😉 I, too, was unaware of the slower metabolism bit . . .

My first pregnancy I cut out coffee in the first trimester. My second pregnancy, I didn’t and ended up miscarring at 7 weeks. Five months later I’m 5 weeks pregnant. I don’t think the caffeine contributed to my miscarriage but at the same time I’m almost afraid to drink it. I know most people would say just give it up its only a couple months but I do enjoy it. I know I will cut back for sure.

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Welcome! I'm the author of The Science of Mom: A Research-Based Guide to Your Baby's First Year, published by Johns Hopkins University Press in 2015. I write about science, health, parenting, and nutrition here and for other print and online outlets.
Find more about me at my website: https://alicecallahanphd.com/

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